Zoro with barrier haki managed to momentarily stop the island busting attack Hakai...proving by the fact that the attack does not go past Zoro.
Luff still hadn't got the hang of barrier back in Udon. He also hadn't used it defensively like Yamato has in Onigashima.
Zoro possessed this ability even before Luffy. He was shooting haki slashes before Wano
so it was better than luffy's pre udon
but luffy has gone a step above that in udon.
unless we get a comparison of an attack luffy fails to block
that zoro could.
then its really up to what you think
I could def see him having stronger armament end of it all
while luffy has better coc and coo.